Scientists have made the startling discovery of a lost world of small archaic humans, who hunted dwarf elephants and Komodo dragons on an Indonesian island as recently as 18,000 years ago. The researchers uncovered the skull and skeleton of an adult human female with a brain the size of a grapefruit and a body the size of a Hobbit. This diminutive new species lived on the tropical island of Flores at the same time that modern humans inhabited nearby islands and were circling the globe. "It is literally jaw-dropping," says anatomist Bernard Wood of George Washington University.

In a report in the 28 October issue of Nature, paleoanthropologist Peter Brown and archaeologist Michael Morwood of the University of New England in Armidale, Australia, and their colleagues at the Indonesian Centre for Archaeology in Jakarta, Indonesia, describe the remains of an adult skull and partial skeleton found last year in the Liang Bua Cave on Flores. This cave woman and the isolated bones of several other individuals are so unlike modern humans that they baptized them as a new species, Homo floresiensis.

The skull looks most like H. erectus--which evolved in Africa about 2 million years ago and spread throughout Asia--except it packs a tiny brain of only 380 cm3, the size of a grapefruit and half the size of the brain of H. erectus specimens found on Java. The skeleton stands at about the same height as the famous australopithecine nicknamed Lucy. The researchers conclude that the Flores female was not deformed or diseased, nor was she a pygmy, dwarf, or midget, whose brains are proportionally large for their bodies.

The leading hypothesis for H. floresiensis's origins is that it was descended from H. erectus, says Brown. He theorizes that during thousands of years of isolation on the islands, the lineage shrank over time as other island mammals did. In a second paper, the authors describe the Lilliputian world of Komodo dragons and dwarf animals, such as a new species of extinct elephant called Stegodon.

Wood and other paleoanthropologists say that the Flores skeleton ranks as one of the most outstanding discoveries of the past 50 years and shows that until recently, modern humans were not alone on the planet. "My [first] reaction was that this is a hoax," says Harvard University paleoanthropologist Daniel Lieberman. "But after I read the paper, I realized it is a normal skull that happens to be very small. There is no apparent evidence for pathology. It is wonderful."